JPH02238367A - Acceleration sensor having flexural beam clamped on one side - Google Patents

Abstract

PURPOSE: To obtain an acceleration sensor with high sensitivity at low cost by a method in which encode generator is structured so that a permanent magnet is provided at one end of a flexible beam of a tape-like amorphous metal thin in a width as compared with the thickness. CONSTITUTION: A housing 1 comprises resin 5 and an airtight case 6 for holding a flexible beam 2 on one side, and a Si oil is filled in a hollow part 7 so that an oscillation of the beam 2 is buffered. The beam 2 is formed with an amorphous metal tape and reacted to a minute acceleration in a vertical direction. It has an extremely high stiffness in a lateral direction. A tape thickness d is about 30μm and a width b is about 3mm. One end of the bending beam 2 is embedded in a resinous body 5 and the other end is freely oscillated. A permanent magnet 3 is adhered to a free end as an inertia mass. The beam 2 is an amorphous metal having magnetism and the permanent magnet 3 can be attracted to the beam by a magnetic tension force. The deformation (bending) of the permanent magnet 3 is measured by a sensor element 4, etc., showing a Hall effect, and converted into a corresponding electric signal. With this structure, it is possible to obtain an acceleration sensor at low cost with static and dynamic strengths and high sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention provides a permanent magnet which is arranged in a housing and is provided at its free end with an inertial mass and at least one permanent magnet which acts as a signal generator or signal forming member. a flexure beam clamped at the side, the flexure beam being flexible in the plane of the acceleration to be measured relative to the sensor housing;
It further comprises a measurement system for determining the deflection, the measurement system comprising a permanent magnet and one or more magnetic field sensitive position sensors (so-called elementary sensors) coupled to the housing.
The present invention relates to an acceleration sensor that has a ntary sensor) and is capable of measuring the position or change of a permanent magnet.

[Prior art and its problems] German patent specification (DIE) No. 28 29 425C
2 +. : C The above type of acceleration sensor is described. Within the sealed housing, a vibration sensitive mass is suspended from a leaf spring that is clamped on one side within the housing. This vibration-sensitive mass is arranged at the free end of the clamped leaf spring and comprises a movable iron part which, when deflected, cuts the magnetic field of a permanent magnet fixed to the housing at the level of this free end. When this mass is deflected, an electrical signal is created by the two magnetic field sensitive electrical resistors.

This electrical resistance is formed in particular by a magnetoresistance, which is symmetrical to the zero position of the sensitive mass and which is equal to the flux of the magnetic field in the gap between the permanent magnet or the pole plate of the permanent magnet and the sensitive mass. Placed perpendicular to the direction of movement.

Furthermore, it is possible to use a permanent magnet as the vibration-sensitive mass instead of the movable iron member, in which case the movable iron member is fixed to the housing.

Obtaining usable measurement signals with such devices in the case of small accelerations requires large manufacturing efforts. The force required to deflect the leaf spring is relatively large, and this force is sensed by a sensitive mass of the required size. It is highly desirable to be able to select the deflection in a given direction of ITl. Such sensors are therefore not suitable for mass production, for example for use in motor vehicle control systems, which require a large number of sensors that are generally similar and are dependent on manufacturing costs.

German Patent Specification (DI?) No. 31 33 050C
2 shows a similar bending beam sensor. A bending beam in the form of an elastic arm clamped on one side made of epoxy resin, vinyl chloride or beryllium copper is arranged in the closed housing and screwed to this housing. The free end of this elastic arm is loaded with a load. In the lower part, i.e. near the point fixed to the housing, the elastic arm is surrounded by a coil. The portion of the resilient arm disposed within the coil comprises a flat member of amorphous metal with low remanence. The elastic arm is deflected by acceleration or vibration, and this deflection creates a tensile or compressive stress in the low remanence member, and an electrical signal corresponding to this stress is generated in the coil. This signal is electronically converted into an acceleration or deceleration value. Such sensors are also very expensive, especially if high measurement accuracy and constant sensitivity are required.

Furthermore, the published German patent application (DE) No. 301e
The vehicle deceleration measuring device described in OOIAI has a leaf spring clamped on one side, at its free end an inertial mass is arranged, and a bar magnet is arranged on this inertial mass. The change in position of the bar magnet is determined by a Hall element. A second permanent magnet is fixed to the housing to detect the voltage across the Hall element when the bending beam is deflected, and this voltage increases linearly with deflection.

The present invention has a particularly simple structure, low manufacturing cost, high static and dynamic strength (repetitive fatigue strength and fatigue strength),
It is an object of the present invention to provide an acceleration sensor that can withstand overload and has high measurement accuracy and measurement sensitivity in the measurement direction. The stiffness in the lateral direction should be high and therefore the sensitivity in the lateral direction to distortions, i.e. the 71pj constant, should be low.

[Means for Solving the Problems, Actions and Effects] The acceleration sensor of the present invention that achieves the above object is arranged in a housing, and has an inertial mass and at least one signal generator or signal forming member at its free end. a flexure beam provided with a permanent magnet and clamped on one side, the flexure beam being flexible in the plane of the acceleration to be measured relative to the sensor housing and further determining the deflection;
This measuring system is equipped with a permanent magnet and
an acceleration sensor having one or more magnetic field sensitive position sensors coupled to a housing by which the position or change of a permanent magnet can be determined; It is characterized by being made of a tape-shaped amorphous metal.

According to the invention, an acceleration sensor that meets high requirements and can be produced at low cost is obtained by means of a single-layer or multi-layer flexural beam, which flexure beam is capable of measuring acceleration in one direction with extremely high sensitivity and precision. reacts linearly to
It has very high bending resistance in the lateral direction. A ratio of bending resistance in the transverse axis to bending resistance in the working plane of 1:4000 is easily achieved. This property is achieved by a thin tape of amorphous metal, and the magnetic properties of this metal do not affect most embodiments of the invention. Due to the sensitivity of extremely thin amorphous metals, it is sufficient to place small permanent magnets as inertial masses and signal-forming members at the free ends of the deflection beams. When the deflecting beam is deflected, this permanent magnet forms a signal corresponding to the acceleration to a position sensor located at a suitable location within or on the sensor housing.

According to an advantageous embodiment of the invention, the thickness of the tape-shaped flexible beam is in the range 10 to 80 μm, preferably in the range 20 to 30 μm, and its width is in the range 1 to 10 mm, preferably in the range 2 to 4 mm.

In this regard, the thickness-to-width ratio of the flexible beam is preferably in the range 1:50 to 1:1000, preferably in the range 1:50 to 1:200.

According to another preferred embodiment of the invention, the flexure beam comprises a multi-layer structure with two or more parallel amorphous metal tapes, integrally held rigidly on the clamp side within the housing. A permanent magnet is placed on the surface of the free end of the tape, and the magnetic force forces the tape together and holds it together. One permanent magnet may be placed on the surface of each multilayer flexure beam, or alternatively, a permanent magnet may be placed on one side and a ferromagnetic iron member on the other side.

Preferably, the permanent magnets and ferromagnetic members are glued onto the flexure beam.

Preferably, one side or surface of the amorphous metal is rougher than the other, and these sides overlap to obtain the highest possible damping effect when the tapes of the multilayer flexural beam move relative to each other.

In another embodiment of the invention, the flexure beam comprises two tapes of amorphous metal that are clamped and held rigidly together, and between the free ends of the flexure beam, these tapes are A permanent magnet is attached to one of the tapes, and the other tape is attached by the magnetic force of this permanent magnet. As the flexure beam flexes, vibrations are damped by the movement of the tape, which is magnetically attached to the permanent magnets.

In addition to frictional damping between the faces of each tape of a multilayer flexural beam, or between a flexural beam and a permanent magnet attached to one of the tapes, the present invention allows for air damping. This is because the flexure beam is arranged in a closed housing such that a very narrow gap is formed between the flexure beam and the housing wall, and this gap inhibits air exchange when the flexure beam is deflected, thereby This is to buffer the vibrations of the bending beam with air.

Furthermore, such air damping alone may be used in multilayer flexural beams.

On the other hand, it is also possible to fill the sensor housing with a conventional buffer fluid, such as silicone oil, to dampen the vibrations of the flexure beam.

The permanent magnet of the deflecting beam of the acceleration sensor of the present invention has a plate-like or block-like structure and is arranged at the free end of the deflecting beam. A Hall element, magnetoresistive, magnetoresistive sensor or other magnetic field sensitive sensor is arranged as a magnetic field sensitive position sensor in the sensor housing, parallel to the deflecting beam, below or above the deflecting beam. In other embodiments, the position sensor is fixed at the front of the sensor housing or to the side thereof at the level of the front free 01° of the deflection beam. Furthermore, the position sensor can be provided on the outer wall or outside the sensor housing in the region of the magnetic flux of the permanent magnet which oscillates according to the deflection beam.

Other features, advantages and applications of the invention will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawings.

[Example] As shown in FIG. 1, the acceleration sensor of the present invention includes a housing 1, a deflection beam 2, and measurement systems 3, 4.
This measuring system consists of a signal generator or a signal forming element 3.
That is, it includes a permanent magnet and a position sensor called a so-called cable sensor 4. The associated electronics for evaluating the electrical signals are not shown for reasons of clarity.

The sensor housing 1 comprises a resin body part 5 holding a flexure beam 2 integrally clamped on one side, and a sealed casing 6, which immerses the flexure beam 2 in silicone oil and absorbs vibrations. The entire hollow space 7 can be filled with silicone oil to cushion the .

The flexure beam 2 is formed from a thin tape of amorphous metal, which responds to very small accelerations in one direction. In the case of the illustrated acceleration sensor, this direction is along the plane of the protrusion. On the other hand, it has extremely high bending resistance in the lateral direction, that is, in the direction perpendicular to the plane of the protrusion. The thickness d of the tape is approximately 30 μm, the width b (perpendicular to the plane of the protrusion) is 3 mm, and the resistance to bending around the stiffness axis is approximately 30 μm. For example, the ratio of the resistances can be 1:4000. Furthermore, when oscillating in the direction of the stiffness (vertical axis), the risk of tilting of the so-called bending beam (instability problem) is mathematically estimated to provide sufficient distance for lateral excitation due to oscillation. be able to.

The bending beam 2 is embedded in the resin body 5 on one side and can vibrate freely on the other end. The permanent magnet 3 is fixed as an inertial mass and as a signal generator on its free end, for example with adhesive. If the beam 2 is formed of an amorphous metal, this metal is magnetic and the permanent magnet 3
can be attached to the bending beam 2 with its magnetic attraction.

The deflection of the bending beam 2, in particular of the permanent magnet 3 arranged at the free end of the bending beam, is measured by a position sensor 4 with a Hall effect sensor element or a magnetoresistive resistor and converted into a corresponding electrical signal. Ru.

Figure 2 shows a bending beam 2' with a permanent magnet 3 arranged at its free end.
shows an embodiment of the invention in which oscillates between two position sensors 4, 4'. Therefore, in both position sensors 4.4' the signals change in opposite directions when the bending beam 2' is deflected. This makes it easier to evaluate the signal or distinguish between interfering signals and usable signals, increasing the operational reliability (redundancy) of the acceleration sensor. In other respects, there is no fundamental difference from the acceleration sensor shown in FIG.

As shown in FIG. 3, in an embodiment of the invention a bending beam 8
A position sensor 9 is provided on the front side of the free end of. If the position of the permanent magnet 10 arranged at the free end of the bending beam 8 changes due to acceleration, an evaluation signal is generated at the position sensor 9 arranged on the front side.

In addition to the position sensor 9 placed on the front side, there is also a position sensor 1
1, 12 can be provided, these position sensors 11, 12, in order to make the signals formed more clear,
It is provided on one or both of the upper and lower sides of the vibration direction. These sensors 11,12 are shown in dashed lines in FIG. 3 and may be unnecessary depending on the application.

Furthermore, in many cases the position sensor is arranged outside the sensor housing 1 or outside its casing 6, if the change in the magnetic field can be measured outside the sensor housing when the position of the permanent magnets 3, 10 changes. It is beneficial to do so.

As shown in FIG. 4.1, in an embodiment of the invention a multilayer bending beam is provided with two or more tapes 13, 14 made of amorphous metal arranged parallel to each other.

4 and 2 show an enlarged view of the free ends of the bending beams 13 and 14 separated.

This arrangement reduces vibration "frictional damping"(1'r
lctlon damping). The parallel tapes 13, 14 are integrally embedded on the clamping side 15 in the resin body 5 and held firmly. At the free ends of the bending beams 13 and 14 two tapes 13.1
4 are pressed together and held together by magnetic force.

For this reason, a permanent magnet 16 is glued to one surface. This permanent magnet magnetically attracts the opposing member, namely the ferromagnetic body part 17 which is abutted against the surfaces of the free ends of the bending beams 13 and 14. Therefore the bending beam 13
and 14, the two layers or tapes 13, 14 arranged one above the other move relative to each other, thereby creating the required frictional damping effect.

Each of the two tapes 13, 14 has surfaces with different roughness, and the rough surfaces can be placed opposite each other to achieve a more effective damping effect, and this rough surface has a glossy surface on the other side. However, it may have a matte appearance.

As long as costs are reasonable, it is desirable that the surfaces of the tapes 13, 14 placed one above the other be roughened.

In this embodiment, the elementary sensor 18 is placed on one side of the bending beam. Note that it is also possible to use the embodiment shown in FIG.

FIG. 5 differs from the embodiment of FIG. 4 only in that, instead of the ferromagnetic body member 17, a second permanent magnet 19 is provided as a reaction member. These two permanent magnets 16, 19 are arranged so as to attract each other.

In the embodiment of FIG. 6, the bending beam is made of two amorphous metal tapes 20 integrally embedded in the resin body portion
．． 21. In this case, the permanent magnet 22 is placed at the free end of the bending beams 20 and 21 between the two tapes 20.21. A permanent magnet 22 is firmly attached to one of the two tapes and magnetically attached to the other tape. In this case, the vibration damping effect is achieved by a frictional force between the permanent magnets 22 and a magnetically attached tape that moves over the permanent magnets 22 when the bending beams 20 and 21 are deflected. arise.

It is also possible to further deform or change the shape in order to create frictional damping.

Figures 7.1 and 7.2 show two variants of the acceleration sensor, in which the vibrations are reduced to "air tti" (alr d).
aa+ping) Attenuates by itself or by adding. As shown in the cross-sectional view of Figure 7.1, this sensor is similar to that of Figure 1 above. However, as shown in FIG. 7.2, in this case the housing 24 in which the bending beam 23 is arranged has a particularly inner width B that extends beyond the bending beam 23.
When the bending beam 23 is deflected at rest and due to acceleration, a very narrow gap L is formed between the walls 25, 26 and the front wall 27. On the other hand, the gap L is very small, and when the bending beam is deflected within this closed housing 24, the air flow through this gap is constricted, thereby damping vibrations. By adjusting this gap, the damping effect can be adjusted to the desired value.

If necessary, the above-mentioned frictional damping and air damping can be combined to easily obtain the desired damping characteristics of the acceleration sensor.

[Brief explanation of drawings]

FIG. 1 is a simplified sectional view of an acceleration sensor according to an embodiment of the present invention, FIG. 2 is a simplified sectional view of an acceleration sensor according to another embodiment in which position sensors are arranged facing each other, and FIG. 3 is a simplified sectional view of an acceleration sensor according to an embodiment of the present invention. Figure 4.1 is a cross-sectional view similar to Figure M1 of an acceleration sensor with a sensor placed in the front, Figure 4.1 is a view similar to Figure 1 of an acceleration sensor with a multilayer bending beam, Figure 4.2 is a permanent magnet and opposing member. FIG. 5 is a cross-sectional view of a sensor similar to FIG. 4 with two permanent magnets at the free end; FIG. Cross-sectional view of a two-layer bending beam with permanent magnets arranged in the seventh,
FIG. 1 is a sectional view parallel to the vibration plane of a sensor that performs air buffering, and FIG. 7.2 is a sectional view taken along line A-A in FIG. 761 and perpendicular to the vibration plane. 1...Housing, 2.2', 8.13 and 14,
20 and 21.23...Bending beam < 3.10,1
6,19.22...Permanent magnet, 4.4' 9...
Position sensor, 5... Resin body part, 6... Sealed casing, 7... Hollow space, 13, 14, 20.2
1... Tape, 18... Elementary sensor. Applicant's agent Patent attorney Takehiko SuzueFIG. 7.1 8-l4 FIG. 7. 2

Claims (17)

[Claims] (1) a flexure beam disposed within the housing, provided with an inertial mass at its free end and at least one permanent magnet acting as a signal generator or signal-forming member, and clamped on one side; A measuring system is flexible in the plane of the acceleration to be measured relative to the housing and further comprises a measuring system for determining deflection, the measuring system comprising a permanent magnet and one or more magnetic field sensitive position sensors coupled to the housing. an acceleration sensor comprising: a position or a change in a permanent magnet;
20, 21, and 23) are acceleration sensors formed of amorphous metal (metallic glass) having a thin tape shape that is wider than the thickness (d). (2) Said tape-shaped flexure beam (2, 2', 8, 1
The thickness (d) of 3 and 14, 20 and 21, 23) is 10
The width (b) is in the range of 1 to 10 mm, preferably in the range of 20 to 30 μm, and
Acceleration sensor according to claim 1, preferably in the range of 2 to 4 mm. (3) The ratio of the thickness (d) to the width (b) of the deflecting beam is in the range of 1:50 to 1:1000, preferably 1:50.
3. The acceleration sensor according to claim 1, wherein the acceleration is in the range of 1:200 to 1:200. (4) Said deflection beams (13 and 14, 20 and 21)
has a multi-layer structure with two or more parallel and amorphous metal tapes (13, 14, 20, 21) held firmly together on the clamping side (15) within the housing (1) and permanently Acceleration sensor according to any one of claims 1 to 3, characterized in that the magnets (16, 19) are arranged on the surface of this tape at the free end of the deflecting beam, each said tape being held together by magnetic forces pressed together. . (5) A permanent magnet (
16) is arranged, and a ferromagnetic material (1
7) The acceleration sensor according to claim 4, wherein: (6) Permanent magnets (16, 19) are arranged on the free outer surface of the multilayer deflecting beam, respectively on opposite sides.
Acceleration sensor listed. (7) The acceleration sensor according to any one of claims 4 to 6, wherein one or both of the permanent magnets (16, 17) and the ferromagnetic material (17) are bonded. (8) The acceleration sensor according to any one of claims 4 to 7, wherein the tapes (13, 14, 20, 21) have matte surfaces or rough surfaces that are relatively matte and are placed on top of each other. (9) The acceleration sensor according to any one of claims 4 to 7, wherein the surfaces of the tapes arranged above each other are formed into rough surfaces. (10) Two amorphous metals arranged parallel to each other
1 . The flexible beams ( 20 , 21 ) formed of two tapes are held together rigidly in the clamp ( 15 ), and a permanent magnet is held between them at the free end of the flexible beam. 1 .
The acceleration sensor according to any one of 3 to 3. (11) The acceleration sensor according to claim 10, wherein the permanent magnet is glued to one side of the tape and magnetically attached to the other side. (12) The flexure beam (23) is placed within the hermetically sealed housing (24) to ensure that a very narrow air gap (L) is formed between the interface between the flexure beam and the housing walls (25, 26, 27). 1 . The air gap throttles the air flow when the deflecting beam ( 23 ) is deflected, thus damping the vibrations of the deflecting beam ( 23 ).
The acceleration sensor according to any one of 11 to 11. (13) Inside the sensor housing (1) there is a deflection beam (
2, 2', 8), wherein the damping fluid, for example silicone oil, is filled in order to dampen the vibrations of 2, 2', 8).
1. The acceleration sensor according to any one of 1. (14) The permanent magnets (3, 10, 16, 19, 22) have a plate-like or block-like shape, and the flexure beams (2, 2
14. The acceleration sensor according to any one of claims 1 to 13, wherein the acceleration sensor is disposed at the free end of each of the parts 1, 20, 21, 23). (15) Magnetic field sensitive position sensor (4, 4', 9, 11, 1
A Hall element, magnetoresistive sensor or other magnetic field sensitive sensor is provided as a flexure beam (2, 18) below or above the flexure beam in the sensor housing.
15. The acceleration sensor according to any one of claims 1 to 14, wherein the acceleration sensor is arranged parallel to the angles 1, 2, and 14). 16. Acceleration sensor according to claim 1, wherein the position sensor (9) is arranged in the sensor housing (6) in front or laterally at the level of the plane of the free end of the deflecting beam (8). . (17) The position sensor can be mounted on the outer wall or the sensor housing (
1, 24), permanent magnets (3, 10, 16, 19)
, 22).
The acceleration sensor according to any one of the above.